Means and method for reproducing sound from sound films



May 6, 1941. R. GC'JRISCH MEANS AND METHOD FOR REPRODUCING SOUND FROM SOUND FILMS Filed Nov. 10, 1939 Rolf 66k W ATTORNEYS Patented May 6, 1941 2340;695 MEANS AND METHOD SOUND FROM Rolf Giirisch, Dresden,

Zeiss Ikon Aktiengesel many FOR REPRODUCIN G SOUND FILMS Germany, assignor to lschaft, Dresden, Ger- Application November 10, 1939, Serial No. 303,859

InG

ermany November 11, 1938 12 Claims. (O1. l79-100.3)

The invention relates to means and a method for reproducing sound from sound records on films and particularly is directed to a method for selectively reproducing sound recorded on films in the form of normal single sound tracks and in the 3 form of balanced double sound tracks. The reproduction of the sound is effected by means of a scanning system including two photo cell circuits.

Scanning systems which include two photo cell circuits and in which the photo cells are arranged electrically or optically in parallel for scanning single sound tracks, while the photo cells are arranged in opposition for scanning balanced double sound tracks have been employed heretofore. The previously employed scanning systems, however, have the great disadvantage that the balancing control for the two photo cell circuits for adjusting the same to the same sensitiveness can only take place before the film is projected. It is not possible to adjust any deviations during the projection of the film, which deviations or differences are caused by errors or fiaws in the film, or variations in the illumination of the scanning slot due to an exchange of the sound lamp.

The principal object of the invention is to overcome this disadvantage of the prior scanning systems and to provide a method and means for reproducing sound selectively from normal single track sound record and balanced double track sound records by means of a scanning system including two photo cell circuits and whose distinguishing feature is that the photo cells can be controlled and balanced during the movement of the sound track carrier, i. e. the sound film, through the reproduction device.

The method of the present invention makes it possible, without any diificulties, to correct the adjustment of the photo cell circuits during the projection of the sound film, which corrections may consist in an adjustment of the voltage supply to the photo cells or in the path of light of the scanning beam, without interrupting the projection of the film or causing a noticeable delay of the same. In particular, it is possible to compensate immediately any variations in symmetry which may be caused by fluctuations within the path of scanning, in the photo cell circuits, or by fiuctua tions in the primary amplifier.

According to a preferred embodiment of a system the invention for practicing the new method two photo cell circuits are connected both to the grid of two primary amplifiers, and in the output circuit of each primary amplifier, which are connected with the input circuit of a power amplifier, are arranged means for controlling and indicating the compensation of the photo cells. These controlling means consist preferably of measuring instruments or loudspeakers or both. In order to control the scanning system during the projection of the sound film, the power amplifier is selectively connected with one of the primary amplifiers, and the other primary amplifier which is not connected to the power amplifier is employed for controlling and compensating the photo cells.

The drawing illustrates diagrammatically a preferred embodiment of a system for practicing the method of the present invention.

The beam of light S after having passed through the sound record on the film, is subdivided by the beam separating means consisting in the present instance of two prisms 2 and 3. The divided light beams S and S are then directed by means of mirrors l and 4 to the photo cells P1 and P2 respectively. The photo cells P1 and P2 are provided each with an operating potential derived from a direct current source 5, which operating potential may be varied by adjusting the resistances 6 and 1 respectively.

The balancing of the two photo cells P1 and P: is obtained by slidably adjusting a common contact member 8 along the two resistances B and l, or by means of any other well known means not illustrated. Both photo cell circuits are connected by means of condensers 9, I3, II and I2 with the grid electrodes of the input tubes V1, V2, V3, V4 of the primary amplifiers. The anode circuits of the tubes V1 and V2 are arranged in opposition, while the anode circuits of the tube V3 and V4 are arranged in parallel. The required grid potential, which determines the working point of the individual tubes, is supplied by the direct cur. rent sources I! and I8 and is conducted to the grid electrodes over the resistances l3, l4 and I 5, 16 respectively.

The two tubes V1 and V2, which are arranged in opposition, receive their operating voltage from a direct current source 21 over a control loudspeaker 2d, a milliammeter 23 and the resistances 25, 26. The anode circuit of the primary amplifier V1, V2 is then connected by means of coupling condensers 28 and 29 with a suitable translating device T, which in turn by means of the switch 30 is adapted to be connected with the power amplifier P which supplies the loudspeaker 32.

The other two tubes V3 and V4, which are connected in parallel, are supplied in similar manner with their operating voltage from the source 21 over a control loudspeaker 22, a milliammeter 2| for alternating current and a resistance l9. A

coupling condenser 20 connects the anode circuits of the last named two tubes with a suitable translating device T, which by means of the switch 30 may be connected to the power amplifier P.

The operation of the device is as follows:

When a balanced double sound track record is scanned, the primary amplifier containing the tubes V1 and V2 will be connected with the power amplifier P by connecting the contact lever C of switch 30 with the switch contact B. Since the grid electrodes of the tubes V3 and V4 are also connected with the photo cell circuits, they will also be influenced by the opposed impulses. The anodes of the other two tubes V3 and V4, are connected, however, in parallel, and therefore the alternating current impulses transmitting speech should compensate each other in the anode circuits of the tubes V3 and V4 when the photo cell circuits are properly balanced. In order to obtain this result, the slidable contact member 8 is adjusted until the alternating current milliammeter 2! indicates zero.

When 'a normal single track sound film is scanned, a complete balance of the photo cell circuits is not as necessary as when a balanced double sound track film is scanned. The two photo cells I and .2 may be considered as being arranged in parallel, because they are influenced by the same light impulses at the same time. The tubes V1, V2 and V3 and V4 may also be considered as being'arranged in parallel. By conmeeting the contact lever C of the switch 30 with the contact A the amplifier with the tubes V3 and V4 is connected with the power amplifier P. Since the grid electrodes of the tubes V1 and V2 may be considered as being arranged in parallel, while their anode circuits are arranged in opposition a balanced condition is obtained by employing the same method as when balanced double sound records are scanned, namely by slidably adjusting the contact member 8 until the. alternating current milliammeter 23 indicates zero.

Since, however, it is only possible to adjust the milliammeter to zero when the sound is recorded in so calledA-type, the balancing of the photo cell circuits is controlled by listening to the control loudspeakers 22 and 24 when the sound is recorded in so called B-type because in the latter case it is more convenient to adjust to the lowest amplitude by listening rather thanwatching the pointer of measuring instrument.

T The invention is not limited to the above clescribed system which represents only a preferred embodiment of the invention. Numerous modification may be adopted within the scope of the invention. It is possible for instance, without difiiculties, to combine the two primary amplifiers, so as to save on tubes and other equipment.

It is also possible with the systemof the present invention to compensate time difierences in phase which may occur when employing additional condensers in the system.

Furthermore, the control means may be arranged in the output circuit of a multistage primary amplifier or between two successive stages of a primary amplifier.

What I claim is:

1. A method of selectively reproducing sound from single track sound film and balanced double track sound films by means of scanning the sound rack with a beam of light which energizes two photo cells, each of which being arranged in its own circuit, including the step of balancing the two photo cells during the scan ning of the sound track without interrupting the movement of the sound film by connecting both photo cell circuits to the grid electrodes of two amplifiers whose anode circuits are arranged in push-pull and parallel respectively, and adjusting the currents in said photo cell circuits until the current in the anode circuits of the amplifiers arranged in parallel is substantially zero.

2. In a system for selectively reproducing sound from single sound track film and balanced double sound track films, scanning means including two photo cells, each of which being arranged in its own cincuit, two primary amplifiers, means for connecting both photo cell circuits with the grid electrodes of said amplifiers so as to: be arranged with respect to one of said amplifiers in opposition and with respect to the other amplifier in parallel, and manually adjustalble means common to both photo cell circuits for balancing said photo cell circuits.

3. In a system for selectively reproducing sound from singlesound track film and a balanced double sound track film, scanning means including two photo cells, each of which being arranged in its own circuit, manually operable means common to both said circuits for balancing the two photo cells, two primary amplifiers, each comprising at least one amplifier tube having a grid electrode and an anode electrode, means for connecting both photo cell circuits with the grid electrodes of said amplifier tubes so as to be connected with respect to one of said amplifiers in opposition and with respect to the other amplifier in parallel, a power amplifier, and means for connecting the anode electrodes of said primary amplifiers with the input of said power amplifier.

4. In a system for selectively reproducing sound from single sound track film and a bal anced double sound track film, scanning means including two photo cells, each of which being arranged in its own circuit, manually operable means common to both said circuits for balancing the two photo cells, two primary amplifiers, each comprising at least one amplifier tube having a grid electrode and an anode electrode, means for connecting both photo cell circuits with the grid electrodes of said amplifier tubes so as to be connected with respect to one of said amplifiers in opposition and with respect to the other amplifier in parallel, means connected with said anode electrodes of said amplifier tubes forming an output circuit, and means in said output circuit for indicating whether or not the photo cell circuits are balanced.

5. In a system for selectively reproducing sound from single sound track film and a balanced double sound track film, scanning means including two photo cells, each of which being arranged in'its own circuit, manually operable means common to both said circuits for balancing the two photocells, two primary amplifiers, each comprising at least one amplifier tube having a grid electrode and an anode electrode, means for connecting both photo cell circuits with the grid electrodes of said amplifier tubes so as to be connected with respect to one of said amplifiers in opposition and with respect to the other amplifier in'parallel, means connected with said anode electrodes of said amplifier tubes forming an output circuit, and means in said output circuit for indicating whether or not the photo cell circuits are balanced, said indicating means comprising an alternating current measuring instrument in each anode circuit of said amplifiers.

6. In a system for selectively reproducing sound from single sound track film and a balanced double sound track film, scanning means including two photo cells, each of which being arranged in its own circuit, manually operable means common to both said circuits for balancing the two photo cells, two primary amplifiers, each comprising at least one amplifier tube having a grid electrode and an anode electrode, means for connecting both photo cell circuits with the grid electrodes of said amplifier tubes so as to be connected with respect to one of said amplifiers in opposition and with respect to the other amplifier in parallel, means connected with said anode electrodes of said amplifier tubes forming an output circuit, and means in said output circuit for indicating whether or not the photo cell circuits are balanced, said indicating means comprising a control loudspeaker in each anode circuit of said amplifiers. I

7. In a system for selectively reproducing sound from single sound track film and a balanced double sound track film, scanning means including two photo cells, each of which being arranged in its own circuit, manually operable means common to both said circuits for balancing the two photo cells, two primary amplifiers, each comprising at least one amplifier tube having a grid electrode and an anode electrode, means for connecting both photo cell circuits with the grid electrodes of said amplifier tubes so as to be connected with respect to one of said amplifiers in opposition and with fier in parallel, means connected with said anode electrodes of said amplifier tubes forming an output circuit, and means in said output circuit for indicating whether or not the photo cell circuits are balanced, said indicating means comprising an alternating current measuring instrument and a control loudspeaker in each anode circuit of said amplifiers.

8. In a system for selectively reproducing sound from single sound track film and a balanced double sound track film, scanning means including two photo cells, each of which being arranged in its own circuit, manually operable means common to both said circuits for balancing the two photo cells, two primary amplifiers, each comprising at least one amplifier tube having a grid electrode and an anode electrode, means for connecting both photo cell circuits with the grid electrodes of said amplifier tubes so as to be connected with respect to one of said amplifiers in opposition and with respect to the other amplifier in parallel, a power amplifier, means for connecting the anode electrodes of said primary amplifiers with the input of said power amplifier, and means in said last named connecting means for indicating whether or not the two photo cell circuits are balanced.

9. In a system for selectively reproducing sound from single sound track film and a balanced double sound track film, scanning means including two photo cells, each of which being arranged in its own circuit, manually operable means common to both said circuits for balancing the two photo cells, two primary amplifiers, each comprising at least one amplifier tube having a grid electrode and an anode electrode, means for connecting both photo cell circuits with the grid electrodes of said amplifier tubes so as to be connected with respect to one of said amplifiers in respect to the other ampliopposition and with respect to the other amplifier in parallel, a power amplifier, means for connecting the anode electrodes of said primary amplifiers with the input of said power amplifier, and means in said last named connecting means for indicating whether or not the two photo cell circuits are balanced, said indicating means comprising an alternating current measuring instrument and a control loudspeaker in each anode circuit of said primary amplifiers.

10. In a system for selectively reproducing sound from single sound track film and a balancing double sound track film, scanning means including two photo cells, each of which being arranged in its own circuit, manually operable means common to both said circuits for balancing the two photo cells, two primary amplifiers, each comprising at least one amplifier tube having a grid electrode and an anode electrode, means for connecting both photo cell circuits with the grid electrodes of said amplifier tubes so as to be connected with respect to one of said amplifiers in opposition and with respect to the other amplifier in parallel, a power amplifier, and switch means for selectively connecting said power amplifier with the output of either one of said primary amplifiers, the primary amplifier not connected to said power amplifier being adapted to be used for indicating whether or not the two photo cell circuits are balanced.

11. In a system for selectively reproducing sound from single sound track film and a balanced double sound track film, scanning means including two photo cells, each of which being arranged in its own circuit, manually operable means common to both said circuits for balancing the two photo cells, two primary amplifiers, each comprising at least one amplifier tube having a grid electrode and an anode electrode, means for connecting both photo cell circuits with the grid electrodes of said amplifier tubes so as to be connected with respect to one of said amplifiers in opposition and with respect to the other amplifier in parallel, a power amplifier, switch means for selectively connecting said power amplifier with the output of either one of said primary amplifiers, and an alternating current measuring instrument in each output circuit of said primary amplifiers, the primary amplifier not connected to said power amplifier being adapted to be used for indicating whether or not the two photo cell circuits are balanced.

12, In a system for selectively reproducing sound from single sound track film and a balanced double sound track film, scanning means including two photo cells, each of which arranged in its own circuit, manually operable means common to both said circuits for balancing the two photo cells, two primary amplifiers, each comprising at least one amplifier tube having a grid electrode and an anode electrode, means for connecting both photo cell circuits with the grid electrodes of said amplifier tubes so as to be con nected with respect to one of said amplifiers in opposition and with respect to the other amplifier in parallel, a power amplifier, switch means for selectively connecting said power amplifier with the output of either one of said primary amplifiers, and a control loudspeaker in each output circuit of said primary amplifiers, the primary amplifier not connected to said power amplifier being adapted to be used for indicating whether or not the two photo cell circuits are balanced.

, ROLF GORISCH. 

